JP2018058081A - Spot shape detection method of pulse laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily determine a laser spot shape.SOLUTION: An inspection wafer (TS) is irradiated with a pulse laser beam of a wavelength having absorptivity. A plurality of laser spots (LS) are formed by this irradiation, and a clearance (S) is interposed between the adjacent laser spots. Afterwards, the laser spot is imaged by imaging means (50), and the contour of the laser spot is extracted from a laser spot image imaged by control means (60), and similarity with the contour of an ideal laser spot shape prestored in storage means (61) is calculated. When the similarity is less than a threshold value, the effect is notified by determining that the laser spot shape is not proper.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a spot shape detection method for a pulse laser beam, which detects the shape of a laser spot formed on a wafer by irradiation with a pulse laser beam.

  In the semiconductor device manufacturing process, a plurality of regions are defined by division lines formed in a lattice shape on the surface of a substantially disc-shaped semiconductor wafer, and devices such as ICs and LSIs are formed in the partitioned regions. . As a method of dividing the semiconductor wafer along the planned dividing line, a laser-processed groove serving as a starting point of breakage is formed by irradiating the wafer with a pulsed laser beam having a wavelength that absorbs the wafer along the planned dividing line. There has been proposed a method of cleaving by applying an external force along a planned dividing line in which a laser processing groove that is a starting point of fracture is formed (see, for example, Patent Document 1).

  In Patent Document 1, a laser beam irradiation means for irradiating a laser beam includes an oscillator that oscillates a laser beam, a condenser that collects the laser beam oscillated by the oscillator and irradiates the wafer, and an oscillator and a condenser. And an optical system for transmitting a laser beam oscillated by an oscillator.

JP 2006-294673 A

  In the laser beam irradiation means, impurities such as debris may adhere to a lens or the like through which the laser beam passes by a condenser or an optical system. In this case, the lens or the like expands due to the attached impurities, and the condensed spot shape is not necessarily condensed into an intended shape such as a circle. As a result, the condensing spot shape of the laser beam is distorted and the desired processing cannot be performed. Therefore, as a method for confirming the processed focused spot shape, a method in which an operator visually checks using a microscope or the like can be considered.

  However, the visual observation by the operator as described above has a problem that the accuracy becomes unstable according to the skill level of the operator and the time required for the confirmation work becomes long.

  This invention is made | formed in view of this point, and makes it one of the objectives to provide the spot shape detection method of the pulse laser beam which can determine a laser spot shape easily.

  The pulse laser beam spot shape detection method according to one aspect of the present invention includes a holding unit that holds a workpiece, a laser beam irradiation unit that irradiates a workpiece held on the holding unit with a laser beam, a holding unit, and a laser beam irradiation unit. A processing feed means for relatively moving in the processing feed direction, an imaging means for imaging the upper surface of the workpiece held by the holding means, and a control means. A laser beam oscillating means for oscillating, a condenser for condensing the pulse laser beam oscillated by the laser beam oscillating means and irradiating the workpiece held by the holding means, and disposed between the laser beam oscillating means and the condenser In a laser processing apparatus comprising an optical system for transmitting a laser beam oscillated by a laser beam oscillation means, A pulse laser beam spot shape detection method for detecting a spot shape of a pulse laser beam oscillated by a means, comprising: an inspection wafer mounting step for mounting an inspection wafer on a holding means; and an inspection wafer mounting step. After the implementation, the focusing point is positioned on the upper surface of the inspection wafer and irradiated with a pulsed laser beam having a wavelength that is absorptive with respect to the inspection wafer and continuously irradiated with a gap between adjacent laser spots, After performing the laser spot forming step for forming a plurality of laser spots and the laser spot forming step, the laser spot is imaged by the imaging means, and the outline of the laser spot is extracted from the laser spot image taken by the control means and stored in advance. The ideal laser spot stored in the instrument When the similarity with the contour of the shape is calculated and the similarity is below the threshold, the determination step determines that the laser spot shape is not appropriate, and the determination step determines that the laser spot shape is not appropriate And an informing step for informing that effect.

  According to this method, since the laser spot is imaged by the imaging unit and it can be determined that the laser spot is not appropriate based on the image captured by the control unit, it is possible to eliminate the confirmation work by the operator. As a result, the accuracy does not change as the operator changes, and the laser spot can be determined stably and easily. Further, the processing time required for the determination can be shortened compared with the visual observation by the operator, and the detection efficiency can be improved.

  Further, in the spot shape detection method of the pulse laser beam, in the laser spot forming step, if the pulse laser beam passes through the optical system and the collector when impurities are attached to the optical system or the collector, the passage path of the pulse laser beam A laser spot may be formed on the inspection wafer after elapse of a predetermined time when the member generates heat and causes expansion.

  According to the present invention, since it can be determined that the laser spot is not appropriate based on the image captured by the control means, the laser spot shape can be easily determined.

It is a perspective view which shows an example of the laser processing apparatus of this Embodiment. It is a block block diagram of the laser beam irradiation means with which the said laser processing apparatus is equipped. It is the elements on larger scale of the wafer in which the laser spot formation step was implemented. It is a flowchart which shows the flow of a process in a determination step. It is a figure which shows the example of the imaging result of a laser spot. It is a figure which shows the example of the imaging result of a laser spot.

  Hereinafter, a spot shape detection method for a pulse laser beam according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a laser processing apparatus according to the present embodiment. The laser processing apparatus used in the pulse laser beam spot shape detection method according to the present embodiment is not limited to the configuration shown in FIG. 1, as long as the wafer can be processed as in the present embodiment. Any processing device may be used.

  As shown in FIG. 1, the laser processing apparatus 1 is provided with a disk-shaped wafer (workpiece) W held on a chuck table (holding means) 3 on a base 2 above the chuck table 3. The laser beam irradiation means 4 is used for processing. The wafer W is divided into a plurality of areas by a plurality of streets ST formed in a lattice pattern on the surface, and devices D such as IC and LSI are formed in the divided areas. A protective tape T made of a synthetic resin sheet is attached to the back surface of the wafer W, and the wafer W is mounted on the annular frame F via the protective tape T. Various wafers can be adopted as long as a laser spot is formed by a pulsed laser beam as will be described later. For example, it may be a semiconductor wafer in which a semiconductor device such as IC or LSI is formed on a semiconductor substrate such as silicon or gallium arsenide, or an optical device wafer in which an optical device such as LED is formed on an inorganic material substrate such as sapphire or silicon carbide. But you can.

  On the surface of the chuck table 3, a holding surface 3 a that sucks and holds the wafer W from the back side is formed of a porous ceramic material. The holding surface 3 a is connected to a suction source (not shown) through a flow path in the chuck table 3. The chuck table 3 has a disk shape, and is provided so as to be rotatable about a disk center by a rotating means (not shown). A pair of clamp portions 9 are provided around the chuck table 3 via support arms. Each clamp portion 9 is driven by an air actuator, whereby the frame F around the semiconductor wafer W is clamped and fixed from both sides in the X-axis direction.

  A cover 11 supported by the cylindrical member 10 is provided below the chuck table 3. The cylindrical member 10 is installed above the index feeding means 13. The index feeding means 13 includes a pair of guide rails 14 and a ball screw 15 that are parallel to the Y-axis direction, and a Y-axis table 16 that is slidably installed on the pair of guide rails 14. A nut portion (not shown) is formed on the back side of the Y-axis table 16, and a ball screw 15 is screwed into the nut portion. The drive motor 17 connected to one end of the ball screw 15 is rotationally driven, so that the Y-axis table 16 is moved along the guide rail 14 in the indexing and feeding direction (Y-axis direction).

  The index feed means 13 is provided on an X-axis table 21 that constitutes the machining feed means 20. The processing feed means 20 further includes a pair of guide rails 22 and a ball screw 23 arranged on the base 2 and parallel to the X-axis direction, and the X-axis table 21 is slidably installed on the pair of guide rails 22. . A nut portion (not shown) is formed on the back side of the X-axis table 21, and a ball screw 23 is screwed to the nut portion. Then, the drive motor 24 connected to one end of the ball screw 23 is rotationally driven, whereby the X-axis table 21 is moved along the guide rail 22 in the machining feed direction (X-axis direction).

  The laser beam irradiation means 4 is provided so as to be movable in the Y axis direction and the Z axis direction above the chuck table 3 by the support mechanism 27. The support mechanism 27 includes a pair of guide rails 28 arranged on the base 2 and parallel to the Y-axis direction, and a motor-driven Y-axis table 29 slidably installed on the pair of guide rails 28. Yes. The Y-axis table 29 is formed in a rectangular shape when viewed from above, and a side wall 30 is erected at one end in the X-axis direction.

  The support mechanism 27 includes a pair of guide rails 32 (only one shown) installed on the wall surface of the side wall portion 30 and parallel to the Z-axis direction, and a Z-axis table slidably installed on the pair of guide rails 32. 33. Further, nut portions (not shown) are formed on the back sides of the Y-axis table 29 and the Z-axis table 33, and ball screws 34 and 35 are screwed to these nut portions. The drive motors 36 and 37 connected to one end of the ball screws 34 and 35 are rotationally driven, so that the laser beam irradiation means 4 is moved along the guide rails 28 and 32 in the Y-axis direction and the Z-axis direction. .

  The laser beam irradiation means 4 includes a cylindrical casing 40 that is cantilevered by the Z-axis table 33, and a condenser 44 attached to the tip of the casing 40. The laser beam irradiation means 4 will be described below with reference to FIG. FIG. 2 is a block diagram of the laser beam irradiation means provided in the laser processing apparatus. As shown in FIG. 2, the laser beam irradiating unit 4 includes a laser beam oscillating unit 42 disposed in the casing 40 of FIG. 1, an optical system 43 for transmitting a pulsed laser beam oscillated by the laser beam oscillating unit 42, and an optical system. 43. A condenser 44 for condensing the pulse laser beam transmitted by 43 and irradiating the wafer W held on the chuck table 3, and a laser beam oscillator 42 disposed between the optical system 43 and the condenser 44. A wavelength conversion mechanism 45 that converts the wavelength of the oscillated pulse laser beam into a short wavelength suitable for processing the wafer W is provided.

  The laser beam oscillation means 42 includes, for example, a pulse laser beam oscillator 421 that oscillates a pulse laser beam having a wavelength of 1064 nm, and a repetition frequency setting means 422 that sets a repetition frequency of the pulse laser beam oscillated by the pulse laser beam oscillator 421. The optical system 43 is disposed between the laser beam oscillation means 42 and the condenser 44. The optical system 43 includes a beam diameter adjuster 431 that adjusts the beam diameter of the pulse laser beam oscillated from the laser beam oscillating means 42, and an output adjusting means that adjusts the output of the pulse laser beam oscillated from the laser beam oscillating means 42 to a predetermined output. 432. The pulse laser beam oscillator 421 and the repetition frequency setting unit 422 of the laser beam oscillation unit 42 and the beam diameter adjuster 431 and the output adjustment unit 432 of the optical system 43 are controlled by the control unit 60 described later.

  The condenser 44 is a direction changing mirror 441 that oscillates from the laser beam oscillating means 42 and is transmitted by the optical system 43 and that changes the direction of the pulse laser beam wavelength-converted by the wavelength converting mechanism 45 described later toward the chuck table 3; A condensing lens 442 that condenses the pulse laser beam whose direction has been changed by the direction conversion mirror 441 and irradiates the wafer W is provided. The wavelength conversion mechanism 45 is disposed between the optical system 43 and the condenser 44. In the wavelength conversion mechanism 45, for example, a pulse laser beam having a wavelength of 1064 nm that has passed through the optical system 43 is converted into a pulse laser beam having a wavelength of 532 nm or 266 nm.

  Returning to FIG. 1, an imaging means 50 is disposed at the front end of the casing 40. The image pickup means 50 is provided so as to be able to pick up an image of the surface area of the wafer W projected with a microscope at a predetermined magnification. The image pickup means 50 includes an image pickup device (not shown) such as a CCD, and the image pickup device is composed of a plurality of pixels so that an electrical signal corresponding to the amount of light received by each pixel can be obtained. Therefore, the imaging unit 50 can detect the street ST by imaging the surface of the wafer W. Based on the captured image of the imaging means 50, the laser beam irradiation means 4 and the wafer W are aligned.

  The laser processing apparatus 1 is provided with a control means 60 that performs overall control of each component of the apparatus. The control means 60 is composed of a processor that executes various processes. In addition to the signal detected by the imaging means 50, detection results from various detectors (not shown) are input to the control means 60. A control signal is output from the control means 60 to the drive motors 17, 24, 36 and 37, the laser beam oscillation means 42 and the like.

  Further, the laser processing apparatus 1 is provided with a storage means 61 for storing various parameters, programs, and the like. The storage means 61 is constituted by a memory. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. The storage means 61 stores data on the contour of the shape of an ideal laser spot LS (see FIG. 3) to be described later, a similarity threshold value to be described later on the contour, and the like.

  Next, a wafer processing method will be described. In the processing method using the laser processing apparatus of the present embodiment, a plurality of laser spots LS (see FIG. 3) are formed at predetermined intervals along the street ST of the wafer W.

  In the processing method of the present embodiment, first, a wafer placement step is performed. In the wafer placement step, the wafer W supported on the annular frame F via the protective tape T is placed on the chuck table 3 shown in FIG. Then, by operating a suction means (not shown), the wafer W is sucked and held on the chuck table 3 via the protective tape T. The frame F is fixed by a clamp 9.

  After the wafer placement step is performed, a laser spot forming step is performed. In the laser spot forming step, first, the chuck table 3 is positioned immediately below the imaging unit 50 by the processing feeding unit 20, and alignment for detecting the processing region of the wafer W to be laser processed is performed by the imaging unit 50 and the control unit 60. . In alignment, image processing such as pattern matching is performed on the street ST of the wafer W picked up by the image pickup means 50 by the control means 60 in order to align the condenser 44 of the laser beam irradiation means 4 and the wafer W. .

  Thereafter, the movement and rotation of the chuck table 3 are controlled based on the calculation result of the control means 60, and the wafer W is positioned so that any one of the orthogonal streets ST extends in parallel with the X-axis direction. Next, the condenser 44 of the laser beam application means 4 is positioned on the street ST parallel to the X-axis direction with respect to the wafer W on the chuck table 3. Further, the focal point of the pulse laser beam irradiated from the condenser 44 is positioned on the upper surface of the wafer W held on the chuck table 3. While the wafer W is irradiated with a pulsed laser beam having an absorptive wavelength from the condenser 44, the chuck table 3 and the condenser 44 are relatively moved in the X-axis direction, which is the machining feed direction, by the machining feed means 20. Moved.

  As a result, as shown in FIG. 3, a plurality of laser spots LS are formed on the upper surface of the wafer W for each pulse pitch based on the wavelength of the pulse laser beam along the street ST. In other words, the gap S is formed between adjacent laser spots LS by continuous irradiation with a pulsed laser beam. FIG. 3 is a partially enlarged view of the wafer subjected to the laser spot forming step. In FIG. 3, the shape of the laser spot LS is formed in a rounded square shape or a long hole shape. However, the shape is not limited to this, and various modifications such as a circular shape, an elliptical shape, and a rectangular shape are possible.

  After forming a plurality of laser spots LS along the target street ST, the irradiation of the pulse laser beam is stopped, and the chuck table 3 and the condenser 44 are relatively moved in the Y-axis direction corresponding to the interval of the street ST. (Index feed). Thereby, the collector 44 can be adjusted to the street ST adjacent to the target street ST. Subsequently, a plurality of laser spots LS are similarly formed along the adjacent streets ST. By repeating this operation, laser spots LS are formed along all the streets ST extending in the X-axis direction, and then the chuck table 3 is rotated by 90 ° around the rotation axis, along the streets ST extending in the Y-axis direction. Thus, a laser spot LS is formed.

  Next, a detection method for detecting the shape of the laser spot LS formed as described above will be described. In this detection method, an inspection wafer is used instead of the wafer W. As the inspection wafer, as long as the laser spot LS can be formed in the same manner as described above, the same wafer W used for manufacturing the product may be used, or a different material (different price) from the wafer W. May be used.

  In the detection method for detecting the shape of the laser spot LS in the present embodiment, the wafer W is changed to an inspection wafer with respect to the processing method, and after the wafer placement step is performed in the same manner as described above, laser spot formation is performed. Steps are performed. Therefore, as the inspection wafer, the reference numeral TS is also written in parentheses on the reference numeral of the wafer W in FIGS. 1 and 3, and the description of the wafer mounting step is omitted. The detection method for detecting the shape of the laser spot LS in the present embodiment is performed in the order of the wafer placement step, the laser spot formation step, the determination step, and the notification step.

  In the laser spot forming step in the detection method for detecting the shape of the laser spot LS, the laser spot LS is formed on the inspection wafer TS in the same manner as the laser spot forming step of the processing method. However, when forming the laser spot LS determined as described later in the determination step, it is required to satisfy the following conditions. The condition is that, when it is assumed that impurities are attached to the optical system 43 or the condenser 44, a plurality of laser spots LS are formed on the inspection wafer TS, and then the pulsed laser beam is condensed into the optical system 43 and the condenser. The laser spot LS is formed until just before a predetermined expansion time elapses when a member (for example, the condensing lens 442) of the passage path of the pulse laser beam generates heat and expands when passing through the device 44. That is, for example, when the expansion time can be empirically specified as 5 minutes, the determination laser spot LS is formed by the determination step until 5 minutes have elapsed after the formation of the plurality of laser spots LS. . Thus, the determination step is performed after the laser spot forming step is performed.

  FIG. 4 is a flowchart showing the flow of processing in the determination step. As shown in FIG. 4, in the determination step, an imaging step SP1, an extraction step SP2, a calculation step SP3, and an appropriate diagnosis step SP4 are performed.

  In the imaging step SP1, a plurality of laser spots LS are positioned immediately below the imaging means 50, and the laser spots LS are imaged by the imaging means 50 at a plurality of locations in the X-axis direction that is the processing feed direction. Examples of the imaging location include the start of irradiation with a pulsed laser beam in the laser spot forming step, an intermediate time from the start to the end of irradiation, and the time immediately before the above-described expansion time when the irradiation ends. The image data of the imaged laser spot LS is input to the control means 60.

  After the imaging step SP1 is performed, the extraction step SP2 is performed. In the extraction step SP2, an appropriate process for extracting the contour of the laser spot LS from the image data of the captured laser spot LS is performed by the control means 60. For example, image processing for extracting the outline of the laser spot LS in a linear manner from the image data of the laser spot LS by a predetermined algorithm is performed.

  After the extraction step SP2 is performed, the calculation step SP3 is performed. Prior to the execution of the calculation step SP3, reference data for the contour that is ideal as the shape of the laser spot LS is stored in the storage means 61 in advance based on the irradiation condition of the pulse laser beam. In the calculation step SP3, the image data of the laser spot LS extracted in the extraction step SP2 and the reference data stored in the storage unit 61 are compared by the control unit 60, and the similarity of the image data with respect to the reference data by pattern matching or the like. Is calculated. The similarity indicates the shift of the image data with respect to the reference data, and the similarity decreases as the shift increases, and increases when the shift is small.

  After the calculation step SP3 is performed, the appropriate diagnosis step SP4 is performed. Before the appropriate diagnosis step SP4 is performed, a threshold value of similarity is stored in the storage unit 61 in advance. As the threshold value, for example, when the shape of the laser spot LS is good, the degree of similarity is almost the same at the start of irradiation of the pulse laser beam in the laser spot forming step and immediately before the expansion time elapses. The degree of similarity is provided in advance as a reference. Further, when the wafer W is broken from the laser spot LS as a starting point, a value between a similarity value when the laser spot LS can function properly as a starting point and a similarity value when the laser spot LS does not function properly. It can be exemplified that a slightly higher value is set. In the appropriate diagnosis step SP4, the similarity calculated in the calculation step SP3 and the threshold stored in the storage unit 61 are compared by the control unit 60. If the similarity is higher than the threshold value, it is determined that the shape of the laser spot LS is appropriate (step SP4: Yes), the shape detection of the laser spot LS is completed, and the process proceeds to processing of the product wafer W. Is done. On the other hand, when the similarity is lower than the threshold value, it is determined that the shape of the laser spot LS is not appropriate (step SP4: No), and a notification step is performed.

  In the notification step, when it is determined that the shape of the laser spot LS is not appropriate as described above, the display unit, the lamp, the alarm, and the like which are not shown in the figure are controlled by the control means 60 to notify that it is not appropriate. At this notification timing, the operator cleans and maintains the optical system 43 and the condenser 44 of the laser beam irradiation means 4 or replaces them with a new optical system 43 and the condenser 44.

  As described above, in the detection method of the present embodiment, the control unit 60 can determine whether or not the shape of the laser spot LS is appropriate based on the imaging result of the laser spot LS. This eliminates the need for visual inspection by the operator, prevents the detection accuracy from becoming unstable due to the skill level of the operator, and allows the shape of the laser spot LS to be detected accurately and stably. Further, the processing time required for the determination can be shortened compared with the visual observation by the operator, and the detection efficiency can be improved.

  In addition, the laser spot LS can be detected by using the imaging means 50 used for the alignment of the wafer W, and it is not necessary to add sensors and imaging equipment for such detection, and the apparatus configuration can be simplified.

  Furthermore, in the laser spot formation step in the detection method of the present embodiment, the above-described expansion time is allowed to elapse before the determination laser spot LS in the determination step is formed. Accordingly, it is possible to avoid the determination that the laser spot LS is appropriate before the constituent portion is expanded even though impurities such as debris are attached to the constituent portion through which the laser beam passes. As a result, it is possible to prevent the laser spot LS from being improperly formed due to heat generation and expansion of the component through which the laser beam passes in the processing of the product wafer W after the determination as appropriate.

  5 and 6 are diagrams illustrating examples of imaging results of laser spots, and represent captured images as diagrams. FIG. 5 shows a laser spot when determined to be appropriate, and FIG. 6 shows a laser spot when determined not appropriate. 5 and 6, (a) is the time when the pulse laser beam irradiation starts and before the above-described expansion time has elapsed, (b) is the intermediate expansion time, (c) is immediately before the expansion time has elapsed, and (a) To (c).

  In FIG. 5, the contour of the laser spot having a vertically long rounded square shape is substantially constant from the start to the end of irradiation, and the laser spot is properly formed. In this case, even if a laser spot is detected as in the above embodiment, the shape of the laser spot is determined to be appropriate in the determination step.

  In FIG. 6, although the contour of the laser spot is appropriate at the irradiation start position, the contour is deformed or distorted as the irradiation of the pulse laser beam proceeds, and the laser spot is not properly formed. This is partly due to the expansion of the lens and the like due to the influence of impurities such as debris on the condenser 44 and the optical system 43 of the laser beam irradiation means 4, and the laser spot shape is not necessarily intended at the start of irradiation when expanded. The light is not condensed into the shape. In this case, when a laser spot is detected as in the above embodiment, it is determined in the determination step that the shape of the laser spot in FIG. Therefore, in the above embodiment, it is possible to easily grasp whether or not an appropriate laser spot can be formed based on the imaging result when the shape of the laser spot is distorted.

  In forming the laser spot as shown in FIGS. 5 and 6 and performing the appropriate diagnosis step as described above, it is assumed that the degree of similarity is set to 80 in the state (a) of FIGS. 5 and 6 (at the start of irradiation). , And a threshold value (70 to 90). At this time, the similarity 79 is shown in FIG. 5B and the similarity 78 is shown in FIG. 5C, and the laser spot shape is determined to be appropriate because it falls within the range of the threshold value (60 to 100). . On the other hand, the degree of similarity is 70 in FIG. 6B, and the degree of similarity is 50 in FIG. 6C, which falls below the threshold (60-100) range immediately before the expansion time of FIG. 6C. It can be determined that the shape of the spot is determined to be inappropriate and maintenance of the lens or the like is necessary.

  The embodiments of the present invention are not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by technological advancement or another derived technique, the method may be used. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea of the present invention.

  In the above embodiment, the similarity with the ideal laser spot shape is calculated using pattern matching in the determination step, but the method of calculating the similarity between the two laser spot shapes can calculate the degree of correlation between them. As long as it is not limited, various methods can be adopted.

  Further, in the laser spot forming step, after the above expansion time has elapsed, the irradiation of the pulse laser beam is resumed to form the laser spot LS. However, when the laser spot shape is deformed by impurities or the like without being affected by the expansion time, The expansion time may not be ensured.

  Moreover, although the case where the imaging means 50 is used for both the detection of the laser spot LS and the alignment of the wafer W has been described, it does not preclude providing a dedicated imaging means for each.

  As described above, the present invention has an effect of easily determining that the laser spot shape is not appropriate, and is useful for detecting the shape of a laser spot formed by irradiating a workpiece with a laser beam. is there.

1 Laser processing equipment 3 Chuck table (holding means)
4 Laser beam irradiation means 20 Processing feed means 42 Laser beam oscillation means 43 Optical system 44 Condenser 50 Imaging means 60 Control means 61 Memory means LS Laser spot S Gap TS Inspection wafer W Wafer (Workpiece)

Claims (2)

Holding means for holding the workpiece, laser beam irradiation means for irradiating the workpiece held by the holding means with a laser beam, and processing for moving the holding means and the laser beam irradiation means relative to each other in the processing feed direction A feeding means; an imaging means for imaging the upper surface of the workpiece held by the holding means; and a control means. The laser beam irradiation means includes a laser beam oscillation means for oscillating a pulse laser beam, and the laser beam oscillation. A condenser for condensing the pulsed laser beam oscillated by the means and irradiating the workpiece held by the holding means; and a laser beam oscillating means disposed between the laser beam oscillating means and the condenser In the laser processing apparatus comprising an optical system for transmitting the laser beam, the pulse laser oscillated by the laser beam oscillation means A spot shape detecting method of the pulsed laser beam for detecting the linear spot shape,
An inspection wafer mounting step of mounting an inspection wafer on the holding means;
After performing the inspection wafer mounting step, a condensing point is positioned on the upper surface of the inspection wafer, and a pulse laser beam having a wavelength that absorbs the inspection wafer is irradiated to form a gap between adjacent laser spots. A laser spot forming step in which a plurality of laser spots are formed by continuously irradiating through
After performing the laser spot forming step, the laser spot is imaged by the imaging means, the contour of the laser spot is extracted from the laser spot image taken by the control means, and an ideal laser stored in the storage means in advance. A step of calculating similarity with the contour of the spot shape, and determining that the laser spot shape is not appropriate when the similarity is below a threshold;
A method for detecting the spot shape of a pulsed laser beam, comprising: a notifying step for notifying the fact when the determining step determines that the laser spot shape is not appropriate. In the laser spot forming step, when impurities are attached to the optical system or the collector, when the pulse laser beam passes through the optical system and the collector, the member in the passage path of the pulse laser beam generates heat and expands. 2. The method of detecting a spot shape of a pulsed laser beam according to claim 1, wherein a laser spot is formed on the inspection wafer after a predetermined time has elapsed.

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